Conventionally, solder alloys containing tin (Sn) have been in use as a brazing filler metal. The brazing filler metal joins electronic components or semiconductor devices to the wiring on a substrate. Or the brazing filler connects semiconductor modules, which package semiconductor devices, to a mounting board. In connecting a semiconductor module to the mounting board, a so-called high-temperature solder (high-melting-point solder), which has a melting temperature higher than that of the brazing filler metal for connecting the semiconductor module to the mounting board, is used. This high-temperature solder is used so that electronic components or semiconductor devices within the semiconductor module may not fall off as a result of the melting of the brazing filler metal used in brazing them.
Also, from the viewpoint of reducing the impacts on the environment or the human body, there has been a tendency to avoid the use of SnPb alloys and promote the development of Pb-free Sn alloy solders which do not contain lead (Pb).    [Patent Document 1] Japanese Unexamined Patent Publication No. 2000-138334.